The present invention relates to capacitive ultrasonic transducers and, more particularly, to capacitive ultrasonic sensors and display devices using the capacitive ultrasonic sensors.
With the rapid development in the industry of display devices, touch panels such as pen tablets have been widely applicable to personal digital assistants (PDAs), personal computers (PCs) and other electrical appliances. Generally, a touch panel may include one of a resistor-type, capacitor-type, surface acoustic wave type and infrared refractive type writing panel. Such touch panels in operation may require a direct touch thereon or may allow signal input at a relatively small distance therefrom, for example, hundreds of micrometers. These touch panels thus may not be user-friendly. Furthermore, scratches or slurs resulting from an inappropriate force applied to the panel or a polluted input source may deteriorate the display quality of the panel. Moreover, the touch panels may only support signal input at a two-dimensional (2D) plane, which may inappropriately limit the signal flexibility. Accordingly, non-touch panels that may allow a user to operate at a given distance without touching the panel have been developed. However, some non-touch panels may be disadvantageous in that the distance may be fixed and not flexible. Furthermore, some non-touch panels may be liable to background light and may suffer from relatively low response speed.
It may therefore be desirable to have a panel that is able to allow signal input at a relatively large distance. It may also be desirable to have a panel that is able to detect signal input at a 2D plane and the distance of the signal from the 2D plane, thereby providing information on a three-dimensional (3D) orientation of the signal, including the 2D location related to the signal and the distance of the signal from the panel.